Site Feedback: How As-Built Inspections Changed with AR Inspections!

Table of Contents

• The importance of as-built inspections and traditional challenges

• What is AR inspection? (remote attendance and high-precision AR)

• How will as-built inspections change with AR technology?

• Site feedback: effects of introducing AR inspection

• Main benefits brought by AR introduction

• Simple surveying with LRTK

• FAQ

The importance of as-built inspections and traditional challenges

As-built inspection is the process in civil engineering and construction of verifying and recording that completed structures and shaped ground are finished to the shapes and dimensions specified in the design drawings. It is a critical process that checks the workmanship at completion (or at intermediate stages) to guarantee quality, and it is a prerequisite for client acceptance and handover. Because it is difficult to modify a structure after completion, it is essential to measure and record accurately during as-built inspections.

Traditionally, as-built inspections were performed manually using tools such as tape measures, leveling staffs, levels, and total stations, with measurements taken point by point and recorded on paper drawings or ledgers. However, this method has presented various challenges on sites.

• Labor shortage and skill transfer issues: There is a shortage of experienced surveyors and as-built measurement technicians, so a limited number of personnel must measure many points, placing a heavy burden on site staff. If experienced staff are not present, there can be concerns about measurement accuracy.

• Cumbersome work and low efficiency: Manual tape measurements and leveling generally require two or more people and involve complex setup. Measuring and recording height and width point by point takes time; measuring a wide area can take an entire day or more. Work is also affected by weather, often forcing interruptions in rain, making it inefficient.

• Limited measurement points and risk of oversights: Manual work physically limits how many points can be measured, so only key spots of the site are measured. Small defects or variations outside major points can go unnoticed and later be flagged in inspections. The larger the structure, the more likely fine deviations will be overlooked by manual measurement.

• Incomplete records and poor utilization: Managing measurement results on paper forms or photo ledgers can lead to missed information later and makes sharing difficult. For example, if the location of buried utilities is not photographed, it may be impossible to verify after completion and could lead to trouble. Paper records are hard to share among stakeholders, and the valuable as-built data collected often remains unused and buried instead of being applied to subsequent work or maintenance.

As described above, traditional methods have limits in both efficiency and accuracy, and the introduction of digital technologies to make as-built inspections more reliable and labor-saving has long been demanded on sites.

What is AR inspection? (remote attendance and high-precision AR)

Recently, a promising solution to these challenges is as-built inspection using AR (augmented reality), so-called "AR inspection." This method overlays digital information such as 3D models from design drawings and reference lines onto the real scene through a smartphone or tablet camera, allowing on-the-spot verification of construction results. When virtual lines and models align precisely with the real scene, inspectors can intuitively confirm conformity without mentally comparing drawings and the actual object.

However, ordinary smartphone AR has GPS errors on the order of several meters, making it unsuitable for construction management and inspection. The solution is RTK-enabled AR, which combines smartphone AR with high-precision positioning using RTK-GNSS. By using RTK technology to apply real-time corrections to satellite positioning errors, smartphone AR positional offsets can be reduced to a few centimeters, enabling near-perfect alignment of design data and reality. This makes it possible to display AR on site with centimeter-level accuracy (half-inch accuracy), bringing AR inspection to a practical level.

Another important keyword is remote attendance. As the name implies, remote attendance refers to inspecting and confirming construction work remotely without physically visiting the site. Promoted as part of the Ministry of Land, Infrastructure, Transport and Tourism’s on-site DX initiatives, it began to be applied as a rule for centrally managed projects from fiscal 2022. Previously, remote verification mainly used wearable or fixed cameras, but introduction of AR technology has further advanced remote attendance. Site staff can relay the AR screen from a tablet, and supervisors in the office can view the feed to see the design models and measurement information overlaid on the site in real time. Because AR-displayed information makes the situation immediately clear—more so than simple video—remote decision-making and instructions become easier.

In short, AR inspection combines high-precision AR positioning with remote attendance to create a next-generation inspection method that "digitizes the entire site so you can peek in from the office." This technology, which enables real-time quality checks across the boundary between site and office, is expected to become commonplace going forward.

How will as-built inspections change with AR technology?

So what concrete changes occur on-site when AR technology is introduced? Here are some specific changes.

First, it becomes possible to verify as-built conditions immediately. For example, where previously a surveyor had to measure heights and thicknesses on site and later compare them with drawings in the office after work completion, AR allows on-the-spot comparison with design data. When a completed 3D model or reference lines are overlaid on the real object on a smartphone or tablet screen, you can instantly judge whether the structure matches the design right after construction. For embankment work on roads, you can use AR to project the design elevation line onto the ground, and while the embankment work is ongoing, add soil until that line disappears—achieving the design value exactly. Even after finishing, overlaying the completed terrain and the design model in the camera view lets you catch small depressions or deficiencies. Errors of a few centimeters (a few in) that were previously overlooked can now be identified at a glance in AR, allowing immediate additional fill or removal to be instructed and executed on the spot.

Also, the inspection cycle itself speeds up. AR as-built checks are completed on site, greatly reducing time spent taking measurements back to the office for organization and analysis. In cloud-linked systems, measurement results are automatically saved and shared, so post-inspection report creation is smooth. With measurement, verification, and recording linked in real time, waiting time between measuring and receiving results is almost zero.

Furthermore, remote as-built inspections become realistic. Combining remote attendance with AR lets inspectors who are not on-site evaluate as-built conditions from the office. For example, site staff can live-stream the AR display of the completed model and the real object from a tablet, and the client’s inspector can watch and give real-time instructions such as "add X cm more fill" or "confirm that height here." Where inspectors had to travel to the site for each inspection in the past, AR inspection allows zero travel time and inspection of multiple sites on the same day. In sites that introduced remote AR inspections, reports indicate that "inspection work time was drastically reduced compared to before" and "one project yielded tens of hours of efficiency gains." AR technology is thus transforming the inspection process itself.

Site feedback: effects of introducing AR inspection

Sites that have introduced AR inspection report various positive feedback. Here are some examples.

On one civil engineering site, displaying the design drawings as AR on-site allowed construction mistakes to be corrected immediately, preventing rework and waste of materials later. "You can see misalignments on the screen at a glance without comparing drawings and the real thing, so even millimeter-level errors could be caught and corrected," said a site supervisor.

Even sites staffed mainly by young employees with little experience operating surveying equipment have seen results. A field staff member from an adopting company said, "Young staff alone were able to carry out surveying and stakeout without issue." Because following AR guidance enables accurate layout and inspection without relying on veteran intuition, it has helped mitigate the shortage of skilled personnel.

Additionally, data management and reporting efficiency have been noticeably improved on-site. At another site, they commented, "Because records go to the cloud in real time, reporting work has become easier." Measurement data and photos are automatically shared to the cloud, eliminating the need to recompile paperwork back at the office and greatly saving time.

Client-side inspectors also reported that "while in the office, they can handle inspections of multiple sites per day." Remote attendance reduces travel burden, allowing a single supervisor to check multiple projects in parallel. This enables efficient inspections without quality loss, even with limited personnel.

From these site voices, it is clear that AR inspection brings tremendous effects to as-built inspections: early detection and correction of construction errors, workflows operable by mainly young staff, streamlined reporting, and mitigation of labor shortages, among other benefits.

Main benefits brought by AR introduction

By introducing AR technology, the following benefits can be expected at as-built inspection and construction management sites.

• Operational efficiency and labor saving: It dramatically shortens the time and effort required for surveying, layout, and as-built verification. Following AR navigation enables work along the shortest path and, in some cases, allows one person to perform tasks that used to require multiple people. For example, stakeout layout that used to take several people half a day can reportedly be completed quickly by one person, representing dramatic efficiency gains. This leads to reduced labor costs and shorter schedules.

• Improved measurement accuracy: RTK-enabled high-precision GNSS achieves centimeter-level positioning accuracy, greatly increasing the reliability of positional information displayed in AR. Lines and design models can be projected on-site without misalignment, enabling previously difficult detailed as-built management. Accurate inspection and surveying backed by data are possible without relying on veteran intuition.

• Improved safety: AR use can reduce the risk of workers entering hazardous areas. For example, layout tasks within areas of heavy machinery operation can be guided from a safe remote location via AR display, avoiding the need to approach. Measurements at height or on scaffolding can sometimes be replaced by remote confirmation, directly contributing to worker safety. Fewer site visits also reduce travel-related accident risks, raising overall safety management levels.

• Smoother communication and consensus building: Digital information can be shared intuitively on-site, improving communication among stakeholders. For clients, prime contractors, and even local residents, projecting the completed image or property boundary with AR on-site has the effect of "seeing is believing." Spatial impressions that are hard to convey with drawings alone can be shared, preventing misunderstandings that lead to rework or complaints.

• Data utilization and promotion of on-site DX: Introducing RTK-enabled AR significantly advances site digitalization. With positioning data, point cloud scans, and photo records managed centrally in the cloud, the burden of data organization after returning to the office is reduced. Accumulated data can be used for analyses combined with BIM/CIM models or for automatic generation of as-built documentation, driving DX across operations. On-site use of 3D data is also a growing requirement in public works, and such initiatives contribute to strengthening a company’s competitiveness.

Simple surveying with LRTK

Finally, as a solution to easily implement RTK-enabled AR on-site, we introduce LRTK. LRTK is an all-in-one on-site DX tool that enables centimeter-accuracy surveying (half-inch accuracy) and high-precision AR display with just one smartphone. By attaching a palm-sized dedicated RTK-GNSS receiver to a smartphone and launching the app, an ordinary smartphone instantly becomes a high-precision surveying instrument and AR device. Complicated initial setup and marker placement are unnecessary—turn it on and you can immediately use high-precision AR.

With LRTK, you upload design data and survey reference data to the cloud in advance and sync them with on-site devices. For example, if you register a coordinate list for stakeout, selecting it on-site starts AR stakeout navigation, and virtual stake display or guidance to the target position can be done easily by anyone. Likewise, you can import alignment data from drawings to display boundary lines and elevation references in AR, or overlay point cloud data captured after construction onto the design model to check as-built differences on the spot—advanced operations are possible. These operations are provided via an intuitive UI and are designed so that non-specialist surveyors can use them.

By completing everything from surveying measurements to AR visualization with just a smartphone, LRTK enables a one-device-per-person setup on-site. Tasks that previously required separate equipment and software (surveying, layout, as-built scanning, photo records, design verification, etc.) can be integrated on a single platform with LRTK, achieving dramatic efficiency gains. Users who introduced LRTK reported that "newcomers handled everything from surveying to stakeout" and "real-time data sharing simplified report creation," and the fact that it is easy to introduce without expensive dedicated equipment is another attractive point. Because it is accessible for small contractors and local governments that were previously distant from ICT construction, LRTK is an ideal first step for on-site DX.

Thus, simple surveying with LRTK revolutionizes traditional surveying and as-built management. With just a smartphone and a compact GNSS device, anyone can handle centimeter-level positioning, dramatically improving on-site surveying accuracy and operational efficiency. Without relying on specialists or costly equipment, one smartphone per person can handle coordinate measurement, stakeout guidance, and as-built inspection, enabling advanced construction management even with few staff. This easy, high-precision surveying solution provided by LRTK will surely advance on-site DX and open the way to next-generation smart construction.

FAQ

Q: What equipment is needed to introduce AR? A: Basically, you can start with a smartphone or tablet capable of AR display. GPS functionality is important for accurate outdoor positioning, but for higher-precision AR inspection, an RTK-GNSS receiver is useful. For example, using a small GNSS unit that mounts on a phone (like an LRTK-type device) allows AR to be used with centimeter-level accuracy (half-inch accuracy). However, dedicated AR apps or software may also be required depending on the purpose, so choose tools suited to your use case.

Q: Is specialized knowledge required to use AR on site? A: No. Recent AR solutions are designed to be usable without advanced expertise. For example, smartphone-based systems like LRTK provide intuitive operation screens, and site staff who are comfortable with basic smartphone operations can perform surveying and AR display. They can be deployed on-site with only simple training, without needing experts in surveying instruments or CAD software.

Q: What is the difference between ordinary smartphone AR and RTK-enabled AR? A: General smartphone AR, which relies only on GPS and gyroscopes, can have errors of several meters, which is unacceptable where high precision is required such as construction management. RTK-enabled AR uses real-time corrections for satellite positioning, reducing errors to a few centimeters and enabling AR accuracy suitable for professional use. This greatly improves alignment between digital information and reality, making it reliable for comparing design drawings and for stakeout tasks.

Q: Can small sites or companies introduce AR technology? A: Yes—small teams especially can benefit from AR technology. Recent AR solutions do not require expensive dedicated equipment and can be used with existing smartphones or tablets and accessible devices. For example, smartphone-based systems like LRTK allow low initial investment and are within reach for small construction companies and municipalities. AR directly addresses labor shortages and operational efficiency, so it can be particularly effective for smaller teams.

Q: Will AR make traditional surveying and construction management unnecessary? A: AR is a tool to support on-site operations, and it does not render traditional surveying and construction management knowledge and experience unnecessary. Correctly interpreting the data AR presents and making quality judgments ultimately still requires the expertise and judgment of technicians. However, AR automates and streamlines many manual measurements and drawing checks, allowing technicians to focus on higher-level decision making and overall optimization. In other words, AR should be positioned as a complement and enhancement to existing techniques, not a replacement.